The present invention is directed generally to the article handling arts and more particularly to a novel and improved rotary type conveyor. While the rotary conveyor of the invention may find other applications, the following description will refer particularly to the use of the invention in conveying a plurality of articles such as can ends through a treatment process such as an oven in which a coating previously applied to the can ends is cured by exposure to air at a predetermined elevated temperature for a predetermined period of time.
In modern can end fabrication operations, a large number of can ends are processed and fabricated at a relatively high rate. To enjoy the economies of scale possible in such a relatively high speed operation, it is important that the can ends be handled accurately and expeditiously. In this regard, the can ends are often conveyed from one portion or station in the fabricating operation to the next in a generally facewise nested condition, in a generally continuous stream or flow. In some instances where it is required that the can ends be handled in a flat condition, that is, such that their surfaces are exposed to be operated upon or treated in some fashion, various conveyor apparatus maybe utilized to convert or turn the can ends individually from their facewise nested condition to a flat, end-to-end condition, in which condition the ends may be fed along a further conveyor belt or the like to or past such further processing stations or apparatus.
In particular, following the initial stamping or formation of the can ends from suitable aluminum or other metallic material or blanks, frequently a tear-away opening portion is formed in the can end. This is frequently accomplished by scoring of the material in the desired shape of the opening and the application of a graspable portion such as a pull ring or tab, or the like. This latter graspable portion is often applied with a rivet which extends through both the graspable portion and the can end.
Following this scoring and tab or ring application, it is often desirable to apply a coating of suitable material to effect "repair" of the product side of the can end, for example to assure that the can end will maintain a seal, and to overcome the effect of any slight perforations or imperfection which may occur as a result of the scoring and application of the pull ring or tab. Various coatings may also be applied in accordance with requirements of a final end user, such as may be appropriate for lining the interior of the can for various applications such as foods and beverages, or other contents which may require a specialized coating in some form.
Such coatings may be applied in a powdered or liquid spray form, and often require a period of heat curing prior to further processing of the can end. Heretofore, it has been the practice to deliver such can ends, following the coating or spraying operation, to a relatively large, cookie-type of oven. Generally speaking the can ends are conveyed through a relatively long "cookie" oven in a flat, end-to-end condition. The speed of the conveyor through the oven, the overall length of the oven and the temperature inside of the oven are all selected to assure proper curing of the coating while the can ends are traversing the oven, and for maintaining the desired rate of can end processing on a number of ends per unit time basis.
However, use of ovens of this type has given rise to a number of problems and shortcomings. For example, these relatively large ovens consume a large amount of heat energy, thus adding considerably to the energy costs of the can end processing operation. Moreover, such ovens are relatively large and relatively long (e.g. on the order of twenty feet or more) and thus take up a relatively large amount of floor space in the processing plant. Floor space is generally at a premium in such operations, and the provision of additional floor space can add considerably to the capital costs and hence the overall costs of the processing operation. Moreover, it has heretofore proven difficult to devise a suitable conveyor system which is capable of reliably conveying the can ends with their product sides exposed for curing, through such an oven at a reliable, controllable speed, over long periods of time. Many rubber or rubber-like belt or conveyor materials fail to withstand the temperatures of the curing oven over long periods of continuous operation. In this regard, it has heretofore been believed necessary to convey the can ends through the oven in a flat, end-to-end condition to assure adequate exposure of the coated surfaces for curing.
Moreover, devising conveyor belts for conveying cans in an upright or on-edge, but spaced apart condition has generally proven difficult. For example, it is generally necessary to provide support at two points about the periphery of the can end to convey it in a generally upright or on-edge position relative to the conveyor. However, given the relatively long length of the curing oven, it has proven difficult to maintain exact positional symmetry as between two supporting belts, which can cause eventual tilting and misalignment of can ends, leading to dislodgement thereof from the belts, and failure to restack properly in a facewise nested condition, upon leaving the oven. Where one or more can ends becomes dislodged during a handling operation carried out at a relatively high rate, many deleterious effects can ensue. For example, dislodged can ends may jam or otherwise jeopardize equipment. A few dislodged can ends may jam in such a manner as to cause many dozens of can ends to similarly become dislodged. Subsequent down time, clean up, repair, etc. is quite costly and detracts from the desired efficiency and economies of such a large scale, high speed operation.